With the ever-increasing popularity of mobile computing, mobile communications is quickly becoming the platform of choice for implementation of network hosts of the future. The trend for convergence between mobile computing and conventional communications networks allows mobile users to enjoy ubiquitous access to network resources irrespective of their current locations. However, the integration of mobile hosts into the existing networks consisting of fixed hosts causes particular problems arising from the specific connectivity requirements of mobile users.
Conventionally, most network application programs employ the Transport Control Protocol/Internet Protocol (TCP/IP) for end-to-end delivery of information amongst various network subscribers. TCP/IP provides each host with a unique communications protocol address (commonly referred to as IP address) which serves to resolve the location and identity of the host. The IP address enables an application running on a host to set up and maintain dialogue with another host on the network.
When at home, a mobile host uses its IP address to communicate with other hosts. However, when away from home, the IP address of the mobile host changes, and the active transmission session between the mobile host and the network may become temporarily lost or disconnected due to the migration of the mobile host from one coverage area to another (handoff). As a result of such breaks in the transmission session, the mobile host is unable to continue corresponding with other hosts in the network.
In recent years, several solutions such as Cellular IP, HAWAII, MIPv4 and MIPv6 have been proposed to provide mobility support in a communications network. These solutions, however, often require mobility support from the underlying network.
Another proposed solution referred to as Indirect-TCP seeks to separate data flow by splitting the transmission session into two separate connections: a first TCP connection between the mobile host and the point of attachment to the network (for example a radio access station), and a second connection between the point of attachment and the corresponding host. By using a link-specific protocol optimized for mobile communications, I-TCP improves the overall performance during handoff. However, I-TCP cannot be readily implemented on existing network platforms as it requires fundamental changes to the TCP/IP protocol.
Accordingly, an important challenge for supporting mobility in TCP/IP resides in handling the IP address changes when a mobile host moves from coverage area to another. In view of the shortcomings of the current networks, there is therefore a need for a technique for reliable routing of data to mobile hosts in a communications network. Preferably, such system would be deal with mobility issues at the application level and may be implemented as an extension of the current network infrastructures, thereby least affecting the architecture of conventional network systems.